1. Field of the Invention
The present invention relates to a haptic feedback input device that provides electrically controlled haptic to an operating member operated by hand, and more particularly, to an absolute position detecting unit that detects a reference position of the operating member.
2. Description of the Related Art
In recent years, various haptic feedback input devices having a force feedback function have been proposed, which integrates the control functions of each controller for a car air conditioner, a car audio, a car navigation system, etc., and supplies feedback force, such as resistance force or thrusting force, to an operating member according to the operating amount or the operating direction of the operating member when a device to be controlled is selected or a function is adjusted by the operating member operated by hand, which provides satisfactory operation feeling and improves the operability of the operating member. In the related art, for example, there has been known a haptic feedback input device including an operating lever, acting as an operating member, free to move; a converting portion that converts the rocking movement of the operating lever into the swinging motions of a pair of driving levers perpendicular to each other; a pair of rotary encoders that detect the swinging amount and the swinging direction of the two driving levers; and a pair of rotary motors that supply feedback force to the operating lever. This device drives the two rotary motors based on output signals from the two rotary encoders to supply desired feedback force to the operating lever via the two driving levers (for example, see Japanese Unexamined Patent Application Publication No. 2003-22159 (pages 5 to 7 and FIG. 1)).
FIG. 10 is a plan view showing the internal structure of the haptic feedback input device disclosed in Patent Document 1. As shown in FIG. 10, a base 100 has first and second rotary motors 101 and 102, and first and second rotary encoders 103 and 104 respectively coupled with rotary shafts of the rotary motors 101 and 102 mounted thereon. The rotary shaft of the first rotary motor 101 is perpendicular to the rotary shaft of the second rotary motor 102, and the first and second rotary encoders 103 and 104 are disposed in the vicinity of an intersection P between the rotary shafts of the two rotary motors 101 and 102. In addition, first and second driving levers 105 and 106 are supported on the base 100 such that they can swing, and an operating lever 108 is coupled with the driving levers 105 and 106 via a driving body 107. The first driving lever 105 can swing around a shaft 105a parallel to the rotary shaft of the first rotary motor 101, and the front end of the first driving lever 105 is formed with a gear portion 105b engaging with a gear 109 fixed to the rotary shaft of the first rotary motor 101. The second driving lever 106 can swing around a shaft 106a parallel to the rotary shaft of the second rotary motor 102, and the front end of the second driving lever 106 is formed with a gear portion 106b engaging with a gear 110 fixed to the rotary shaft of the second rotary motor 102. In addition, the first and second rotary motors 101 and 102 and the first and second rotary encoders 103 and 104 are connected with a control unit, which is not shown in FIG. 10, and the control unit acquires the output signals from the first and second rotary encoders 103 and 104 and outputs desired control signals to the first and second rotary motors 101 and 102.
In the haptic feedback input device having the above-mentioned schematic structure, when an operator moves the operating lever 108 in a certain direction, for example, the Y-Y direction in FIG. 10, the first driving lever 105 swings around the shaft 105a, accordingly the gear 109 and the first rotary encoder 103 are rotated. When the operating lever 108 is moved in the X-X direction, the second driving lever 106 swings around the shaft 106a, accordingly the gear 110 and the second rotary encoder 104 are rotated. Also, when the operating lever 108 is moved in a direction between the X and Y directions, the first and second driving levers 105 and 106 swing respectively, and the first and second rotary encoders are rotated. The control unit acquires the output signals from the rotary encoders 103 and 104, and computes the swinging direction and the swinging amount of the first and second driving levers 105 and 106, that is, the moving direction and the moving amount (moving angle) of the operating lever 108, based on the output signals. Then, the control unit outputs control signals to the first and second rotary motors 101 and 102 based on the computed results. Therefore, desired operation feeling is supplied to the operating lever 108. For example, in a case in which the operating lever 108 is moved in a certain direction at a certain angle, if the first and second rotary motors 101 and 102 are rotated in an opposite direction to the rotary motion of the first and second driving levers 105 and 106, a certain degree of operation force is supplied to the operating lever 108, and the operator operating the operating lever 108 by hand can feel this operation force as a click sense.
In the haptic feedback input device in the related art, the control unit computes the moving direction and the moving amount of the operating lever based on the output signals from the rotary encoders. However, since the rotary encoder outputs two kinds of pulse signals having a phase difference of 90 degrees, the relative displacement amount of the operating lever cannot be detected by using only the output signals of the rotary encoders. Thus, an absolute position detecting unit is required to detect an absolute angle with respect to the reference position of the operating lever.
In the related art, there has been known a technique in which a potentiometer (variable resistor) is used as such an absolute position detecting unit, and the absolute position of the operating lever is computed based on a variation in resistance by operating the potentiometer according to the movement of the operating lever. However, the potentiometer has a problem of durability in that the resistance value easily varies due to abrasion caused by the sliding motion of a brush or the accumulation of abrasion powder with the elapse of time and a detection accuracy problem in that characteristics of a resistor vary easily according to manufacturing conditions.